The usage data - session information (time spent), environment information (OS, et cetera), feature use and exceptions (if any) is stored in a local SQLite database, which is located in the user's roaming profile folder at the following location:

C:\Users\<username>\AppData\Roaming\ICSharpCode\SharpDevelop4.0

The file itself is named usageData.dat. Although the extension is non-standard for SQLite, you can use one of the various SQLite management tools to have a look inside at the information (I am using SQLite3 Management Studio here):

Point it to the database file (please note that the file doesn't exist if you didn't opt in for UDC):

Now you can peruse the tables & information that is stored by UDC (please note that no information will be in the tables once UDC has
uploaded sessions - once data for a session has been uploaded successfully, the associated data is purged locally):

The tables are: Sessions, Environment, Exceptions, FeatureUses as well as Properties. The latter is used to store the client id (see earlier blog post):